<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>计算圆的面积</title>
    <script>
        function circleArea(radius){

            //Math.PI == π
            return Math.PI * radius * radius;
        }

        console.log(circleArea(10));
    </script>
</head>
<body>

</body>
</html>